1. Field of the Invention
The present invention relates to semiconductor devices and, more particularly, to a semiconductor device having a power supply ring and a grounding ring surrounding a semiconductor element.
In recent years, integration of semiconductor devices has been advanced, and the number of electrodes of semiconductor devices has been increased. Accordingly, a demand for reducing a switching noise has been increased, the switching noise being generated when a lot of signals supplied to a semiconductor device are turned on or off at the same time. Such a switching noise is referred to as a simultaneous switching noise. When an electric coupling of the power supply ring and the ground ring is strong, the influence by the simultaneous switching noise becomes large.
2. Description of the Related Art
FIG. 1 is a plan view of a power supply ring and a ground ring of a conventional semiconductor device. In FIG.1, the semiconductor element 1 is provided on an interposer 6 (redistribution layer). A ground ring 2 is formed on the interposer 6 so as to surround the semiconductor element 1. A power supply ring 3 is formed in surroundings of the grounding ring 2. A plurality of bonding pads 4 are formed outside of the power supply ring 3.
Some of the electrode pads 1a of the semiconductor element 1 is electrically connected to the respective bonding pads 4 formed on the interposer 6 by bonding wires 5. Some other electrode pads 1a of the semiconductor element 1 are connected to the ground ring 2 by the bonding wire 5 so as to be grounded. In addition, some other electrode pads 1a of the semiconductor element 1 are connected to the power supply ring 3 by the bonding wires 5 so that an electric power is supplied from the power supply ring to the semiconductor element 1.
FIG. 2 is a plan view of a part of the semiconductor device shown in FIG. 1. Each of the bonding pads 4 is connected to the respective one of the electrode pads 1a by the respective one of the bonding wires 5 (metal wire) as shown in FIG. 2. Similarly, some electrode pads 1a of the semiconductor element 1 are connected to the power supply ring 3 by the respective bonding wires 5. Some other electrode pads 1a of the semiconductor element 1 are connected to the ground ring 2 by the respective bonding wires 5 so as to be grounded.
A voltage of 3V is supplied to the power supply ring 3, for instance, and, thereby, the power supply voltage (3V) is supplied to the electrode pads 1a connected to the power supply ring 3. Additionally, the ground ring 2 is connected to a grounding line, and, thereby, the electrode pads 1a connected to the ground ring 2 are grounded.
In the above-mentioned semiconductor device, the electrode pads 1a are arranged along the four sides of the semiconductor element 1. Each of the ground ring 2 and the power supply ring 3 is configured to be in a square shaped belt so as to encircle the semiconductor element 1 with an irregular space provided therebetween.
In the above-mentioned structure, the ground ring 2 is grounded, and a constant power supply voltage is supplied to the power supply ring 3. Therefore, there is a voltage difference between the ground ring 2 and the power supply ring 3, and the capacitive coupling is provided between the ground ring 2 and the power supply ring 3. Such a capacitive coupling is referred to as a decoupling capacity in general, and indicates a magnitude of the electric coupling between the grounding ring 2 and the power supply ring 3.
High integration and speed-up of the semiconductor devices result in an increase in the number of I/O of semiconductor devices and the frequencies, which causes a problem relates to a noise such as a simultaneous switching noise, a reflection noise or an external noise. Especially, when an electric coupling between the ground potential and the power supply potential is weak, the influence of the above-mentioned noise is greatly increased. A fluctuation in the potential of the ground ring 2 and the power supply ring 3 is caused by the above-mentioned simultaneous switching noise, the reflection noise or the external exogenous noise. The fluctuation in the potential of the ground ring 2 is referred to as a ground bounce, and the fluctuation in the potential of the power supply ring 3 is refereed to as a power supply bounce. When the above-mentioned simultaneous switching noise, the reflection noise and the exogenous noise become large, the power supply bounce and the ground bounce also become large which causes a malfunction of the semiconductor device.
Moreover, the distance between each of the electrode pads 1a and the grounding ring 2 of the semiconductor element 1 is reduced when the size of the semiconductor device is reduced. Similarly, the distance between each of the electrode pads 1a and the power supply ring 3 is reduced, and the distance between the electrode pads 1a and the bonding pads 4 is reduced. In the conventional semiconductor device, as shown in FIG. 2, the bonding wires 5 are provided between the electrode pads 1a of the semiconductor element 1 and each of the ground ring 2, the power supply ring 3 and the bonding pads 4. That is, the bonding wires 5 extend from electrode pads 1a to different three positions. In the above-mentioned structure in which the bonding wires 5 extend between different connection points, there may be a case in which one of the bonding wires 5 come in contact with the adjacent one of the bonding wires 5. Thus, it is necessary to provide a certain distance between different connection points. However, a sufficient distance cannot be provided between the connection pints due to the reduction in the size of the semiconductor device.
Additionally, the number of the bonding pads 4 connected to the electrode pad 1a increases as the number of the electrode pads 1a of the semiconductor element 1 increases. Therefore, the distance between the adjacent bonding pads 4 is reduced, which causes an increase in the cross-talk noise (electromagnetic induction noise) generated between the adjacent bonding pads 4. Especially, a large cross-talk noise is generated at the connection points of the bonding wires 5, which causes a malfunction of the semiconductor device due to the cross-talk noise.
It is a general object of the present invention to provide an improved and useful semiconductor device in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a semiconductor device in which the influence of the simultaneous switching noise is reduced by increasing the decoupling capacity between the ground ring and the power supply ring.
In order to achieve the above-mentioned objects, there is provided according to the present invention a semiconductor device comprising: a semiconductor element having a plurality of electrode pads; a redistribution substrate mounting the semiconductor device; and a power supply pattern and a ground pattern formed on the redistribution substrate in a surrounding area of the semiconductor element, wherein one of the ground pattern and the power supply pattern has a plurality of convex portions protruding toward the other of the ground pattern and the power supply pattern, and the other of the ground pattern and the power supply pattern has a plurality of concave portions each of which receives the corresponding one of the convex portions with a predetermined distance therebetween.
According to the present invention, since the convex portions protrude into the respective concave portions, a length of a gap formed between the ground patter and the power supply pattern is increased. Thereby, the decoupling capacity between the ground pattern and the power supply pattern increases, and a power supply bounce or a ground bounce caused by a simultaneous switching noise or an external noise can be suppressed. Therefore, the semiconductor device can be prevented from malfunctioning due to the simultaneous switching noise.
Additionally, one of the ground pattern and the power supply pattern closer to the bonding pads of the redistribution substrate includes a shielding portion extending between adjacent ones of the bonding pads. Accordingly, the adjacent ones of the bonding pads are shielded from each other, thereby preventing generation of a cross-talk noise between the adjacent ones of the bonding pads.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.